This national study is designed to identify individuals who are at risk of developing Type I Insulin Dependent Diabetes Mellitus (IDDM). The University of Michigan will act as an Affiliated Center in this national multicenter study to screen patients, perform tolerance test and conduct various aspects of the Treatment Protocols in the Diabetes Prevention Trial-Type 1 Diabetes (DPT-1). Those individuals identified will be invited to participate in a national controlled, randomized trial to determine if immunization with insulin can prevent development of IDDM within 5 years. The hypothesis of this study is immunization with insulin may prevent beta cell damage and therefore development of IDDM. The investigators will be affiliated with the University of Colorado Barbara Davis Center for Childhood Diabetes, a clinical coordinating center for this study, which has been approved by the National Institutes of Health.